The EU move to label Hezbollah's military wing a terrorist group is the fruit of a lengthy diplomatic, legal and intelligence campaign.

The European Union's decision to list Hezbollah's military wing as a terrorist organization is the fruit of a lengthy diplomatic, legal and intelligence campaign waged jointly by Israel, Britain, the United States, the Netherlands and Canada. A cache of bombs discovered in Nazareth, a 150-page legal document, and dozens of secret visits and phone calls to various leaders were among the key factors contributing to the decision.

The campaign began after the bombing in Burgas, Bulgaria, last July, which killed five Israeli tourists and one Bulgarian. As intelligence indicating that Hezbollah was to blame accumulated, the Foreign Ministry decided the time was ripe for action.

To this end, it set up a special task force, headed by the ministry's Deputy Director General Jeremy Issacharoff and Shai Cohen, head of the Regional Security and Counterterrorism Department. The team also included representatives of the National Security Council, the Defense Ministry and the intelligence agencies. Similar task forces were set up by Britain's Foreign Office and the U.S. State Department.

One of the task force's first moves was giving various EU countries masses of intelligence that Israel had collected - not just about Hezbollah's role in the Burgas attack, but also about its involvement in Syria's civil war, money laundering, drug smuggling and setting up sleeper cells in Europe. Unusually, the intelligence agencies agreed to this massive transfer of sensitive information.

A senior Foreign Ministry official said that, among other things, Israel passed on intelligence showing that Hezbollah was fighting alongside President Bashar Assad's regime in Syria in early 2013, before this became publicly known.

Israel also gave Berlin information about the assets and bank accounts of 950 Lebanese Shi'ites living in Germany who were suspected of being sleeper agents, or of involvement in transferring money to Hezbollah and helping it with logistics. Similar information was given to Spain, France and Italy.

One move that ultimately proved critical was Israel's decision, immediately after the Burgas attack, to send a forensics team to help investigate.

The Burgas probe, in which the United States, Britain, Germany, Canada and Australia also participated, convinced the Bulgarian government to announce in February 2013 that Hezbollah's military wing was behind the attack.

One key piece of evidence was the large number of phone calls between Burgas and various locations in Lebanon associated with Hezbollah, including calls from phone numbers known to belong to Hezbollah operatives. Another was the forged American driver's license used by one member of the three-man cell, which was traced back to a Beirut printer affiliated with Hezbollah.

The smoking gun, though, was the bomb's composition, including the specific type of plastic explosive used - which proved identical to the composition of 24 bombs discovered by Israeli security services in Nazareth in August 2012. These bombs had been smuggled into the country at Hezbollah's behest by a group of drug smugglers. Later, the bomb's composition also proved an exact match to bombs discovered by Thailand's security services in January 2012, at a warehouse owned by a Hezbollah operative in Bangkok.

The Burgas investigation also uncovered the three perpetrators' identities, but this information was kept secret. The senior Foreign Ministry official said the men are hiding in southern Lebanon, and that Israel is searching for them.

From the start, the ministry official said, the task force knew the biggest obstacle would be translating the accumulated intelligence about Hezbollah into evidence that would stand up in a European court. Several EU countries, first and foremost Germany, said they wouldn't support listing Hezbollah as a terrorist organization unless they were sure their domestic courts wouldn't overturn the decision for lack of evidence.

Consequently, the task force put together a 150-page document detailing all the evidence, as well as its legal significance.

"We didn't just collect all the relevant material for them; we also linked it to European legislation and various [legal] precedents," the official said.

After months of work, the document was completed in May. It was given first to Germany, which at that time was wavering. A few days after the document was hand delivered to Germany's interior minister, members of the task force gave a four-hour briefing to German officials with additional intelligence material.

A week later, on May 22, Germany announced it was ready to blacklist Hezbollah's military wing. This decision convinced several other wavering countries that the evidence was truly solid.

With the legal obstacle surmounted, it was time for the diplomatic campaign to begin.

About six weeks ago, the Foreign Ministry gave all EU ambassadors a detailed briefing on the matter, and Israeli ambassadors in Europe were instructed to do the same for the highest-level officials they could reach - generally, foreign ministers, prime ministers or presidents.

Prime Minister Benjamin Netanyahu and President Shimon Peres also made personal phone calls to the leaders of wavering states, such as Austria, many of which voiced fears that listing Hezbollah as a terrorist organization would destabilize Lebanon and make Hezbollah even more extreme.

"We argued that Hezbollah was already destabilizing Lebanon by its involvement in the Syrian war, its ties with Iran and its possession of tens of thousands of rockets," and that blacklisting it would actually "weaken its power in Lebanon," the senior Foreign Ministry official explained.

Thus, in their calls to countries like Austria, Malta, Greece and Slovakia, Netanyahu and Peres stressed both the Burgas attack and Hezbollah's involvement in Syria.

Washington also exerted heavy diplomatic pressure. U.S. Secretary of State John Kerry and Under Secretary for Political Affairs Wendy Sherman made calls to dozens of senior European officials in recent weeks.

Now that the EU has finally made the decision in principle, the next step is for each member state to enact appropriate legislation, and then to start enforcing it. In theory, blacklisting Hezbollah's military wing means that its money and assets in Europe will be frozen, Europeans will be barred from doing business with it, and its operatives will be denied visas to Europe.

The difficulty, however, lies in distinguishing between its military and political wings, and determining which assets or operatives belong to each. That is why Netanyahu stressed that though Israel welcomes the EU move, it remains opposed to this distinction.